5.6 ETS

5.6 Electron Transport System General Summary NADH & FADH2 from glycolysis & Krebs cycle carry H atoms (p+ & e-) to the ETS; Reduce oxygen to form water and synthesize ATP. ETS consists of enzymes & cytochromes (other proteins) embedded in the inner mitochondrial membrane.

5.6 Electron Transport System e- (from NADH & FADH2 are transferred step by step through an ETS by cytochromes. At each transfer, some energy is released. Some of this energy is used to actively transport H+ out of the matrix into the intermembrane space.

5.6 Electron Transport System Some H+ will diffuse back into the matrix through ATP synthase. The H+ transfers some energy to the ATPsynthase, which then synthesizes ATP from ADP & P. The final cytochrome (e- acceptor) is an enzyme that combines the e- & H+ with O2 to form water.

5.6 Electron Transport System The H from NADH provides enough energy to synthesize 3 ATP molecules. The H from FADH2 only has enough energy to synthesize 2 ATP molecules.

5.6 Electron Transport System ETS Animation

5.6 Electron Transport System Bacteria don’t have mitochondria. Their ETS is in their cell membranes. In some, O2 isn’t the final e- acceptor - depending on the e- acceptor, they can produce H2S or NH3. (anaerobic respiration).

5.6 Electron Transport System Facultative anaerobes – can survive with or without O2, and can switch between fermentation & aerobic respiration Obligate anaerobes – cannot survive with O2, so can only perform fermentation or anaerobic respiration Obligate aerobes – cannot survive long without O2

5.7 Oxygen, Respiration, & Photosynthesis Without O2, cells must perform fermentation - only releases 2 ATP per glucose. As long as O2 is present, we gain more energy from our food. Humans (& other animals) get their O2 from breathing in air, which comes from photosynthesis.

5.7 Oxygen, Respiration, & Photosynthesis

Relating Photosynthesis & Cellular Respiration 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Cellular Respiration: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy The products of photosynthesis are the raw materials for cell respiration & the products of cell respiration are the raw materials for photosynthesis. light

Relating Photosynthesis & Cellular Respiration 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Cellular Respiration: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy Both processes provide carbon skeletons used in biosynthesis & use an ETS to form ATP, but they differ in their energy source. light

Relating Photosynthesis & Cellular Respiration Respiration: Releases chemical energy by reducing oxygen to water & oxidizing sugars to carbon dioxide. Photosynthesis: Stores chemical energy by oxidizing water to oxygen & reducing carbon dioxide to sugar.